From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 83800 invoked by alias); 19 Feb 2018 13:10:41 -0000 Mailing-List: contact gdb-patches-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-patches-owner@sourceware.org Received: (qmail 83791 invoked by uid 89); 19 Feb 2018 13:10:41 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-3.6 required=5.0 tests=AWL,BAYES_00,FREEMAIL_FROM,RCVD_IN_DNSWL_NONE,SPF_PASS autolearn=ham version=3.3.2 spammy= X-HELO: mail-wm0-f47.google.com Received: from mail-wm0-f47.google.com (HELO mail-wm0-f47.google.com) (74.125.82.47) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Mon, 19 Feb 2018 13:10:39 +0000 Received: by mail-wm0-f47.google.com with SMTP id 191so7978993wmm.4 for ; Mon, 19 Feb 2018 05:10:39 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to:cc; bh=/ZprnWK2C0vzLw/g6G/aenTBoTHiynJpHFMhCbFsWGU=; b=ihAC6ZmlbfNWmszO3IeA2iBBYE6cfmV9Re/peWPDHKkzF2nNo6A4IhzpSFsconwwW+ HCXvekcyfOdE7piNkyGYdQbS5W0mvdX/c6dG7eQBqOyW1TKnjKZDdU0qzBHriHJOvTbj kNXEnpdbqCJPR/a2TFFxGBmEaoN72VFRxQqa9aeOhOQp0jPUnm7P8UJiZbYIR5i5Vq/W M24U7XuA+OSwkp1oBOIeZBfe/RjHyqJv+uOeYF5nrL7xkc3Lm2LyrrGrNqjUlCr4Y4oN i8Uj4jsmTpxYQQZL9NpitInmyz3u1F5ulGvoZ02CiE38/2JPkPSgQGJAHmLUWXPIkqq9 mXDA== X-Gm-Message-State: APf1xPAPQQOH5ncQ7QTSQHQ6JUPzcm8eD63eOqyh2pWgmvZC73K4Sudq fOfx75u5KCH3XfCYFURF6j8WSB/NSjFBunLjg/G60Iom X-Google-Smtp-Source: AH8x225Wr9F0iTHALTQUEwecn/4rKhs9DcemgleABohGsfe6HDCxozdgGYMtbR+egdJXWp2Kj7cMWrwhubbTEvGwrRE= X-Received: by 10.80.148.133 with SMTP id s5mr20079983eda.144.1519045837741; Mon, 19 Feb 2018 05:10:37 -0800 (PST) MIME-Version: 1.0 Received: by 10.80.149.245 with HTTP; Mon, 19 Feb 2018 05:10:37 -0800 (PST) In-Reply-To: <8c6e36c70ca0ce3f0980971bfa50c160@polymtl.ca> References: <20180204000647.19188-1-niteria@gmail.com> <20180204000647.19188-2-niteria@gmail.com> <8c6e36c70ca0ce3f0980971bfa50c160@polymtl.ca> From: Bartosz Nitka Date: Mon, 19 Feb 2018 13:10:00 -0000 Message-ID: Subject: Re: [PATCH v3 1/1] Don't rewind PC for GHC generated frames To: Simon Marchi Cc: GDB Patches Content-Type: text/plain; charset="UTF-8" X-SW-Source: 2018-02/txt/msg00243.txt.bz2 Hi Simon, Thanks for taking a look at the updated version. > I hoped there would be some comments from others. Is there anyone we could ask directly? > In particular, is anybody > able to tell if adding a call to find_pc_compunit_symtab in > get_frame_address_in_block is a performance concern? How frequently is > get_frame_address_in_block called, and how costly is find_pc_compunit_symtab > to call? This is a valid concern. When I originally made this change, I was focusing on making dwarf2_frame_cache work. dwarf2_frame_cache calls get_frame_address_in_block and then calls dwarf2_frame_find_quirks. dwarf2_frame_find_quirks calls find_pc_compunit_symtab. That makes me think that for this code path there should be no difference. That's only one code path, I haven't analyzed others. If performance turned out to be a problem, then undoing the effect of get_frame_address_in_block in dwarf2_frame_cache would get me 90% of what I care about currently (unwinding). That said, there must be a way to resolve this in a data driven way. Are there any pre-existing benchmarks I can run? Is there a scenario that I can benchmark to resolve the questions above? > However, please tell me if you are fine with > my suggestion below. Yes, that's a good change. Thanks! If it helps move things along I'm happy to submit an updated version. Thanks, Bartosz